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Abstract:

This relates to a method for manufacturing a shell-like structural
component for a vehicle using additive layer manufacturing. In a step of
the method, a first material is applied to a region of the shell-like
structural component. In another step of the method, the region of the
shell-like structural component is heated by a laser beam such that the
first material is added to the shell-like structural component. The
shell-like structural component comprising the first material is cooled
in another step such that an internal stress is generated within the
shell-like structural component resulting in a bending of the shell-like
structural component. This further relates to a shell-like structural
component which is manufactured by a method using additive layer
manufacturing.

Claims:

1. A method for manufacturing a shell-like structural component for a
vehicle using additive layer manufacturing, comprising: applying a first
material to a region of the shell-like structural component; heating the
region of the shell-like structural component by a laser beam such that
the first material is added to the shell-like structural component; and
cooling the shell-like structural component comprising the first
material, such that an internal stress is generated within the shell-like
structural component resulting in a bending of the shell-like structural
component.

2. The method according to claim 1, further comprising: applying the
first material to a plurality of regions of the shell-like structural
component from different directions.

3. The method according to claim 1, wherein a bending direction is
opposite to a direction of a force which acts on the shell-like
structural component when it is installed in the vehicle, wherein the
force is generated by a cargo unit standing on the shell-like structural
component or by cabin air pressure.

4. The method according to claim 1, further comprising: generating a
layered structure of the shell-like structural component by applying the
first material to the surface of the shell-like structural component,
wherein the layered structure comprises a layer of the first material.

5. The method according to claim 1, wherein the internal stress is
induced using different materials.

6. The method according to claim 1, wherein the internal stress is
induced using different temperatures when heating the region of the
shell-like structural component.

7. The method according to claim 1, wherein the shell-like structural
component is a floor panel.

8. The method according to claim 7, wherein a thickness of the floor
panel is between 2 millimeters and 100 millimeters, preferably between 2
millimeters and 4 millimeters.

9. The method according to claim 1, wherein the first material has a
coefficient of thermal expansion which differs from a coefficient of
thermal expansion of the region of the shell-like structural component to
which the first material is applied.

10. The method according to claim 1, wherein the shell-like structural
component is selected from the group comprising an aircraft cargo floor
panel, a part of an aircraft outer skin, a part of an aircraft wing and a
part of an aircraft door.

11. The method according to claim 1, wherein the first material is
selected from the group comprising silicone, iron, copper, manganese,
chromium, tin, vanadium, titanium, bismuth, gallium, lead, aluminum and
zirconium.

12. The method according to claim 1, wherein additional internal stress
is generated within the shell-like structural component by shot-peening
and flare-fitting.

13. A shell-like structural component for an aircraft in which an
internal stress exists which results in a bending of the shell-like
structural component; wherein a bending direction is opposite to a
direction of a force which acts on the shell-like structural component
when it is installed in the vehicle; wherein the force is generated by a
cargo unit standing on the shell-like structural component or by cabin
air pressure.

14. (canceled)

15. A shell-like structural component according to claim 13 wherein the
shell-like structural component is a floor panel.

16. A shell-like structural component according to claim 13 wherein the
thickness of the floor panel is between 2 millimetres and 100
millimetres.

17. A shell-like structural component according to claim 16 wherein of
the floor panel is between 2 millimetres and 4 millimetres.

18. A shell-like structural component according to claim 15 wherein the
component comprises one of an aircraft cargo floor panel, a part of an
aircraft outer exit, a floor of an aircraft wing, and a part of an
aircraft door.

[0002] The embodiments described herein relate to a manufacturing process
for components of a vehicle. In particular, the embodiment relates to a
method for manufacturing a shell-like structural component for a vehicle
using additive layer manufacturing, a shell-like structural component for
an aircraft manufactured by the method and the use of a shell-like
structural component in an aircraft.

BACKGROUND

[0003] Other objects, desirable features and characteristics will become
apparent from the subsequent summary and detailed description, and the
appended claims, taken in conjunction with the accompanying drawings and
this background.

[0004] Nowadays, there exist many different manufacturing processes for
manufacturing structural components of vehicles. Such manufacturing
processes are in most cases subtractive. For example, subtractive
processes are milling, cutting, machining, drilling, etc. These
subtractive processes may rely on the principle that a certain part of
material is removed from the component in order to change the contours or
the shape of the component which may be assembled in a later step. It is
also possible to remove material, for example on an uneven surface of a
component, such that a high quality of the surface of the component can
be achieved. However, subtractive processes may be limited in their
application since material is removed from the component. In other words,
the material can only be removed as long as sufficient material is left
such that the component can still fulfill stability requirements. For
example, dents or scratches on surfaces may be repaired by removing a
distinct amount of material from the surface such that dents or scratches
on the surface of the component disappear.

[0005] DE 10 2007 015 795 A1 describes a metal-cutting machining process
for a semi-finished product having a predetermined shape and at least one
machining surface. In order to protect the surface of the product during
the process, a foil is affixed on the surface.

[0006] DE 10 2007 026 100 B4 describes a method providing a milling tool
with a cutting depth limiter, where maximum cutting depth of the milling
tool is limited by the limiter. Therein, a surface section is milled
under guidance of the milling tool by the guiding contour. A machining
device for machining a laminated composite material at a surface section
is also provided.

SUMMARY

[0007] According to a first aspect of the present embodiment, a method for
manufacturing a shell-like structural component for a vehicle using
additive layer manufacturing (ALM) is provided. In a step of the method,
a first material is applied to a region of the shell-like structural
component. In another step, the region of the shell-like structural
component is heated by a laser beam such that the first material is added
to the shell-like structural component. In another step of the method,
the shell-like structural component comprising the first material is
cooled such that an internal stress is generated within the shell-like
structural component resulting in a bending of the shell-like structural
component. The internal stress may at least be induced in the region of
the shell-like structural component and/or near the first material which
is comprised by the shell-structural component after cooling. The vehicle
may be an aircraft, a car or a rail vehicle.

[0008] With this method it is possible that the contour or shape of the
shell-like structural component may be adapted in an assembled state, for
example if it is assembled in the vehicle. In other words, the internal
stress which is generated within the shell-like structural component
after applying the first material to the shell-like structural component
induces a stress or force that bends the shell-like structural component
such that a certain or predetermined shape of the shell-like structural
component which comprises the first material may be provided. The
internal stress may be generated by using different materials for the
shell-like structural component and the first material. For example, the
first material may be applied to a surface of the shell-like structural
component or only a part of the surface of the shell-like structural
component. In case the first material is applied to only a part of the
surface of the shell-like structural component, it is possible to induce
internal stresses within the shell-like structural component only in a
region around or near the applied amount of first material on the surface
of the shell-like structural component. In this manner, only a part of
the shell-like structural component may be deformed by the internal
stresses. This deformation may appear as a bending or twisting of the
shell-like structural component. However, the first material may be
applied to distinct locations on the surface of the shell-like structural
component in order to induce internal stresses near these locations such
that the mechanical resistance of the region near the applied first
material is improved.

[0009] The material may also be applied to the shell-like structural
component such that the first material is located within or inside the
shell-like structural component. In other words, first material may not
only be applied to the surface of the shell-like structural component but
also inside the shell-like structural component. This may be achieved by
providing a layered structure in which a layer of the first material is
located between parts of the shell-like structural component. Using
additive layer manufacturing, the different layers may be applied
subsequently.

[0010] When applying the first material to the region of the shell-like
structural component, the first material may be a powder which is
supplied to the region of the shell-like structural component by a powder
supply unit. This powder may be a metallic or non-metallic powder which
is, when applied to the region of the shell-like structural component,
heated and/or melted. By melting the first material and a part or a
region of the shell-like structural component, a connection or continuity
between both the first material and the shell-like structural component
may be achieved; e. g. the first material is mixed with and/or firmly
bonded to the region of the shell-like structural component. For heating
or melting the first material and/or the region of the shell-like
structural component, different methods may be used, such as selective
laser melting (SLM). The heating of the shell-like structural component
and the first material may be provided by a laser beam. The heating of
the region of the shell-like structural component by the laser beam may
be conducted during the application of the first material to the region
of the shell-like structural component. In this manner, it is ensured
that parts of the shell-like structural component within the region are
melted when the first material is applied. By melting the first material
as well as the region of the shell-like structural component, it is
possible that this part or region of the shell-like structural component
may be firmly bonded to the first material such that a continuity between
the first material and shell-like structural component is provided.

[0011] By cooling the shell-like structural component and the first
material, melted parts of the first material as well as the shell-like
structural component may be solidified. After solidification, the
internal stress within the shell-like structural component is generated.
The internal stress being generated after solidification may be limited
to the regions where the first material has been applied to the
shell-like structural component. The internal stress provides an enhanced
mechanical robustness or resistance in the regions within the shell-like
structural component to which the first material has been applied. The
internal stress may also generate a bending force that bends the
shell-like structural component such that it may adopt a predetermined
form or shape.

[0012] The shell-like structural component may be a plate with a curved
surface or only an even plate with no curvature. However, the shell-like
structural component may be a three-dimensional solid which comprises
several materials. The shell-like structural component may be
manufactured from metallic or non-metallic materials. The shell-like
structural component may be a part of a large structural component of the
vehicle. For example, the shell-like structural component is a sidewall
panel that comprises a curved or even surface. It is possible that the
shell-like structural component comprises a thickness of between 5
millimeters whereas its lateral dimensions, e. g. length and width, are
more than one meter. It should be mentioned that the thickness of the
shell-like structural component is equal to or greater than 5
millimeters. For example, the thickness is 100 millimeters. However, the
lateral dimensions are usually much greater than the thickness of the
shell-like structural component. The length and width may be measured
along the curved or even surface of the sell-like structural component.
Generally, the shell or a shell-like structural component is a
three-dimensional structural element with a small thickness when compared
to other dimensions of the structural element. A plate is a
three-dimensional structural element whose thickness is very small when
compared with other dimensions of the structural component. However, the
shell-like structural component may withstand high mechanical loads, such
as a traversing vehicle or passenger.

[0013] According to an embodiment, the first material is applied to a
plurality of regions of the shell-like structural component from
different directions.

[0014] This can be achieved by using a multi-direction additive
manufacturing process. It is possible that the first material is applied
from different directions simultaneously such that the time for producing
the shell-like structural component may be reduced and a better
accessibility to every region of the shell-like structural component is
achieved.

[0015] According to another embodiment, a bending direction is opposite to
a direction of a force which acts on the shell-like structural component
when it is installed in the vehicle, wherein the force is generated by a
cargo unit standing on the shell-like structural component or by cabin
air pressure.

[0016] The bending which is due to the internal stress within the
shell-like structural component generates a deflection of at least a part
of the shell-like structural component. In other words, the shell-like
structural component may be curved such that a convex shape and therefore
a deflection in a direction which is substantially parallel to the
thickness of the shell-like structural component is provided. The
deflection of the shell-like structural component may be much smaller
than its width or length. The deflection is dependent on the thickness of
the shell-like structural component and/or on the distance between the
supports of the shell-like structural component. If the shell-like
structural component is supported by two beams, which will be described
in the detailed description of the figures, the deflection of the
shell-like structural component is dependent on the distance between the
beams and on the thickness of the shell-like structural component.
Moreover, the force may act on the surface of the shell-like structural
component in a direction which is opposite to the deflection of the
shell-like structural component. In this manner, the deflection of the
shell-like structural component is reduced. In particular, the bending of
the shell-like structural component by the internal stress is directed
opposite to a load direction which may occur during operation of the
vehicle. Such loads or forces may be pressure forces for example. In
other words, the force may be generated by a cabin pressure or a pressure
difference between the cabin pressure and the environmental pressure
during flight of an aircraft. The forces may also be generated by a mass
of a cargo loading unit which is placed on the shell-like structural
component or the dead load of the shell-like structural component.
However, the force may be a gravitational force. The bending direction is
a direction into which at least a part of the shell-like structural
component is deflected when relative to attachment points of the
shell-like structural component. For example, if two edges of the
shell-like structural component are fixed by attachments or bearings, the
deflection of the part of the shell-like structural component that is
between the attachments or bearings indicates the direction of the
bending of the shell-like structural component. A similar case is shown
in more detail in the description of the drawings.

[0017] According to another embodiment, a layered structure of the
shell-like structural component is generated by applying the first
material to the surface of the shell-like structural component. The
layered structure comprises a layer of the first material and the
shell-like structural component.

[0018] The thickness of the layer of the first material may be the same at
every region on the surface of the shell-like structural component, but
it may also vary such that different thicknesses of the layer of the
first material occur at different regions on the surface of the
shell-like structural component. There may also be more than one or two
layers of the first material. For example, there may be a plurality of
layers of the first material as well as a plurality of layers of the
shell-like structural component such that the layered structure is
composed by many different layers. However, layers of other materials may
additionally be added to the layer of the first material and/or to the
shell-like structural component.

[0019] For example, the layer of the first material is applied to two
different sides, e. g. on the surfaces of the shell-like structural
component such that the shell-like structural component is arranged
between both layers of the first material. In this case, the first
material is applied to the shell-like structural component by heating
both the shell-like structural component and the first material. After
cooling the layered structure comprising the shell-like structural
component and the two layers of first material, internal stresses may
occur as a result of different thermal expansion characteristics of the
first material and the shell-like structural component. In other words,
the first material and the shell-like structural component may have
different coefficients of thermal expansion such that the first material
contracts faster than the shell-like structural component and vice versa.
In case the first material contracts faster than the shell-like
structural component, this is, the first material has a higher
coefficient of thermal expansion than the shell-like structural
component, a tensile stress occurs within the first material whereas a
compression stress occurs within the shell-like structural component.
Such different coefficients of thermal expansion of the different
materials which are connected to each other lead to tensile stresses or
compression stresses which deform or bend the shell-like structural
component. Therefore, it is necessary that these materials are firmly
connected.

[0020] According to another embodiment, the internal stress is induced
using different materials.

[0021] For example, the shell-like structural component comprises another
material than the first material which is applied to the shell-like
structural component. If both the first material and the shell-like
structural component comprise different coefficients of thermal
expansion, internal stresses may be generated within regions or near
regions to which the first material has been applied to the shell-like
structural component when the temperature changes. However, internal
stresses may also be generated by adjusting the amount of first material
which is applied to the shell-like structural component. In other words,
the more first material is applied to the shell-like structural
component, the more the shell-like structural component will be
influenced by the material characteristics of the first material.

[0022] According to another embodiment, the internal stress is induced
using different temperatures when heating the region of the shell-like
structural component.

[0023] In other words, the different material characteristics of the
shell-like structural component and the other materials which are applied
to the shell-like structural component may be influenced by a heat
treatment. The heat treatment may be conducted such that only these parts
or regions of the shell-like structural component are heated to which the
first material is applied. Generally, the heat treatment using different
temperatures or different materials provides the opportunity that after
cooling the shell-like structural component and the other materials
applied to the shell-like structural component internal stresses are
generated such that the bending of the shell-like structural component
itself or in combination with the first material is generated. The heat
treatment or the arrangement of different materials at the shell-like
structural component may be adjusted such that a predetermined bending of
the shell-like structural component itself or in combination with the
first material or other materials applied to the shell-like structural
component can be achieved.

[0024] According to yet another embodiment, the shell-like structural
component is a floor panel. For example, the floor panel is installed in
an aircraft as a passenger floor panel or a cargo floor panel.

[0025] After manufacturing the shell-like structural component, e.g. after
cooling the shell-like structural component, it may be assembled to other
components as to form a part of a vehicle. The first material may
therefore be a part of the shell-like structural component. After
manufacturing the shell-like structural component, it comprises the first
material since it is firmly bonded to the shell-like structural
component. For example, the shell-like structural component is a floor
panel of the vehicle. The floor panel should have an even surface with no
curvature, such as a plate. In a loaded condition, the floor panel is
usually bent. This bending is defined by a deflection of parts of the
floor panel from a neutral line. By using the described manufacturing
method, it is possible that the shell-like structural component comprises
a predefined bending due to internal stresses such that the deflection of
the floor panel is directed into a direction which is opposite to a
direction of a force in a loaded condition of the floor panel. This means
that the floor panel is deflected in an opposite direction of the loading
direction such that the deflection of the floor panel is reduced or
vanishes when the force is applied in a loaded condition.

[0026] According to another embodiment, a thickness of the floor panel is
between 2 millimeters and 4 millimeters. For example, the floor panel is
integrated in a cargo space or a passenger cabin.

[0027] Preferably, the thickness of the floor panel is 3 millimeters. The
floor panel may comprise different layers of material, e. g. a layered
structure, but it may also comprise different alloys with different
material characteristics, such as different coefficients of thermal
expansion.

[0028] According to another embodiment, the first material has a
coefficient of thermal expansion which differs from a coefficient of
thermal expansion of at least the region of the shell-like structural
component to which the first material has been applied.

[0029] Using materials with different coefficients of thermal expansion
generates internal stresses after firmly bonding the materials and
changing the temperatures of the connected materials. In other words,
both the first material and the shell-like structural component comprise
different coefficients of thermal expansion such that internal stresses
are generated due to the different expansion characteristics of the
shell-like structural component and the first material. This principle
may also be applied to various other materials which are combined to the
shell-like structural component and/or the first material. Connecting or
firmly bonding two different materials each having an own coefficient of
thermal expansion, results in internal stresses occurring as tensile
stresses and compression stresses.

[0030] According to another embodiment, the shell-like structural
component is selected from the group comprising an aircraft cargo floor
panel, a part of an aircraft outer skin, a part of an aircraft wing and a
part of an aircraft door.

[0031] The cargo floor panel of the aircraft may have a thickness of
preferably 3 millimeters. The cargo floor panel may be deflected in an
unloaded condition due to the internal stresses generated within the
shell-like structural component such that, if the cargo floor panel is
loaded, the deflection may be significantly reduced or even vanish. This
aspect will be shown in more detail in the description of the drawings.
The part of the outer skin of the aircraft may be connected to stringers
or ribs such that, in an unloaded condition, the part of the outer skin
is deflected in a region where there is no connection between the part of
the outer skin and the ribs or stringers. Usually in flight, the inner
pressure within the fuselage is higher than the outer pressure of the
aircraft. This difference in pressure during cruise flight generates a
force which pushes the parts of the outer skin, which are not connected
to ribs or stringers, into the direction of the lower pressure, e.g.
outwards or to the outside of the aircraft. Using the shell-like
structural component of the described manufacturing method, results in a
bending or deflection of the part of the outer skin in the direction
opposite to the direction into which the part of the outer skin is pushed
due to the pressure loads. This reduces the deflection of the part of the
outer skin. In this manner, the aerodynamic characteristics of the outer
skin of an aircraft may be positively influenced since no deflections or
reduced deflections at the outer skin occur. The same applies to an
aircraft door, which means that the aircraft door is deflected due to
internal stresses such that, in a loaded condition, for example during
flight, the aircraft door adapts an ideal form, e.g. the aircraft door
may be aligned with the outer skin of the aircraft. Furthermore, an
aircraft wing is bent or deflected in a loaded condition. This means that
the deflection of the aircraft wing during flight differs from the
deflection of the aircraft wing during ground operation. By a bending or
a deflection which is opposite to the loading direction of the wings
during flight, improved flight characteristics can be achieved, for
example a reduced aircraft drag. The deflection which is opposite to the
loading direction of the wing may be induced by internal stresses
generated within the part of the aircraft wing, e. g. the parts of the
wing to which the shell-like structural component has been attached. This
is also explained in more detail in the description of the drawings. If
within the description the word "ideal" is used, it may refer to
advantageous mechanical or aerodynamic characteristics being achieved by
the adaption of certain shapes or contours. Thus, it may mean that
certain mechanical or aerodynamic characteristics or behaviors of
components of the vehicle may be enhanced.

[0032] According to yet another embodiment, the first material is selected
from the group comprising silicon, ion, copper, manganese, chromium, tin,
vanadium, titanium, bismuth, gallium, lead, aluminum and zirconium.

[0033] Furthermore, synthetic materials may also be used for the first
material and/or the shell-like structural component. Alloys comprising
different metallic or non-metallic materials may also be a suitable
composition for the first material and/or the shell-like structural
component. It is possible to use multiple metal or plastic materials for
the manufacturing or printing process to create a shell-like structural
component which comprises different metal or plastic alloys to generate
the needed specific properties at each location of the shell-like
structural component. The needed alloy is produced or generated during
the three-dimensional printing process. It should be noted that the
additive manufacturing of the shell-like structural component may also be
called printing process since the first material is added to the
shell-like-structural component in order obtain the ready-made shell-like
structural component which comprises the first material.

[0034] According to another embodiment, the first material may be applied
to the surface of the shell-like structural component such that an
extrusion protruding on the surface of the shell-like structural
component, e. g. a protrusion on the surface of the shell-like structural
component is provided. These protrusions may be manufactured from a
synthetic material.

[0035] Moreover, the protrusions itself may comprise different materials
which are applied to the surface of the shell-like structural component.
The material or materials may be applied such that a fiber-reinforced
body, for example on the surface of the shell-like structural component,
is generated. Therefore, metal fibers or carbon fibers may be used to
strengthen or reinforce a matrix material, like for instance plastics.
These fiber reinforced materials which are applied or printed to the
surface of the shell-like structural component may reduce crack
propagation within the shell-like structural component. In other words,
the fiber-reinforced protrusions may effectively prevent a further
opening of the crack surfaces. Furthermore, theses protrusions may have
an arbitrarily shaped cross-section, wherein the cross-section is
obtained ether tangentially or perpendicularly to the surface of the
shell-like structural component. An arbitrary cross-section of the
protrusions may be obtained using printing process like selective laser
melting and/or additive layer manufacturing.

[0036] Additionally, the integrated fibers induce a thermal tensioning or
stress within the shell-like structural component due to the different
coefficients of thermal expansion of the different materials such that a
crack initiation is avoided. In other words, the integrated fibers induce
an inherent compressing stress which is induced by different thermal
expansions of the different fiber materials and/or different matrix
materials.

[0037] According to another embodiment, the first material is applied to
the shell-like structural component in a fibrous form. For example, the
protrusions may comprise high-strength fibers. Such protrusions,
especially those comprising fibers, may provide an enhanced fatigue and
damage tolerance.

[0038] According to another embodiment, the shell-like structural
components are used as stiffening means. Such stiffening means may be
used to strengthen certain parts of an aircraft fuselage, for example
corners of a door frame. In this manner, shell-like structural components
may be used at the corners of a door of an aircraft fuselage such that
so-called corner doublers, which are usually integrated at said corners,
may be replaced. The stiffening of the corners may be provided by induced
internal stresses within the shell-like structural components leading to
an improved fatigue and damage tolerance. The shell-like structural
component may be attached near the door of the aircraft, e. g. at the
corners of the door.

[0039] According to another embodiment, a stress within the shell-like
structural component is generated by shot-peening and flare fitting.
Shock-peening is understood as a working process used to produce a
compressive residual stress layer and modify mechanical properties in
components. In this manner, the mechanical properties of the shell-like
structural component may locally be influenced so as to enhance the
durability and robustness of the shell-like structural component. The
stresses generated by flare-fitting may also result in an improvement of
the durability and the mechanical robustness of the shell-like structural
component. Flare fitting is a working process using a mandrel that is
forced into the end of a hole or a tube-like element in order to form a
flare by cold working. For example such holes may be placed within the
shell-like structural component. Flare-fitting generates stresses in a
region around or near the holes or tube-like elements of the shell-like
structural component such that the stresses enhance the durability or
robustness in these regions. It should be mentioned that shock-peening
and flare-fitting may also be used in order to generate a stress within
components, e. g. the shell-like structural component, such that these
components adapt a predetermined shape as a result of the internal
stresses. The adaption of a predetermined shape may occur as a bending of
the component.

[0040] According to another aspect, an internal stress exists within the
shell-like structural component for an aircraft which results in a
bending of the shell-like structural component. A bending direction of
the shell-like structural component is opposite to a direction of a force
which acts on the shell-like structural component when it is installed in
the vehicle. The force is generated by a cargo unit standing on the
shell-like structural component or by cabin air pressure. The internal
stress which exists within the shell-like structural component may be
induced by a working process like additive layer manufacturing, selective
laser melting, shock-peening or flare fitting.

[0041] According to another aspect, a use of a shell-like structural
component on an aircraft is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The various embodiments will hereinafter be described in
conjunction with the following drawing figures, wherein like numerals
denote like elements, and:

[0043] FIG. 1 shows a cross-sectional view of a layered structure with
different materials according to an embodiment.

[0044] FIG. 2 shows a cross-sectional view of a layered structure with
different thicknesses of the layers according to an embodiment.

[0045] FIG. 3 shows a cross-sectional view of a layered structure which is
deformed as a result of internal stresses within the layered structure
according to an embodiment.

[0046] FIG. 4 shows s sectional view of a shell-like structural component
in an unloaded condition and in a loaded condition according to an
embodiment.

[0047] FIG. 5A shows a sectional view of stiffening units and a part of an
outer skin of an aircraft fuselage in an unloaded condition according to
an embodiment.

[0048] FIG. 5B shows a sectional view of stiffening units and a part of an
outer skin of an aircraft fuselage in a loaded condition according to an
embodiment.

[0049] FIG. 6A shows a cross-sectional view of an aircraft fuselage with
an integrated aircraft door in an unloaded condition according to an
embodiment.

[0050] FIG. 6B shows a cross-sectional view of an aircraft fuselage with
an integrated aircraft door in a loaded condition according to an
embodiment.

[0051] FIG. 7A schematically shows an aircraft with aircraft wings in an
unloaded and in a loaded condition according to an embodiment.

[0052] FIG. 7B schematically shows another aircraft with aircraft wings in
an unloaded and in a loaded condition according to an embodiment.

[0053] FIG. 8A schematically shows a side view of an aircraft fuselage in
an unloaded condition according to an embodiment.

[0054] FIG. 8B schematically shows a side view of an aircraft fuselage in
a loaded condition according to an embodiment.

[0055] FIG. 8C schematically shows a side view of an aircraft fuselage in
an unloaded condition according to another embodiment.

[0056] FIG. 9 shows a flow diagram for a method for manufacturing a
shell-like structural component for a vehicle using additive layer
manufacturing.

DETAILED DESCRIPTION

[0057] The following detailed description is merely exemplary in nature
and is not intended to limit the disclosed embodiments or the application
and uses thereof. Furthermore, there is no intention to be bound by any
theory presented in the preceding background detailed description.

[0058] Items shown in the Figures are not drawn to scale. In FIG. 1 a
cross-sectional view of a layered structure 10 with different layers of
material is shown. The layered structure 10 may be at least a part of a
shell-like structural component, which shell-like structural component
may be used in a vehicle such as an aircraft, a car or a rail vehicle.
The shell-like structural component may thus be a part of an outer skin
of an aircraft, a floor panel of an aircraft or a part of a door of an
aircraft. The layered structure 10, which is shown in FIG. 1, comprises
three different material layers. For example, a first layer 1 and a third
layer 3 are made of the same material and a second layer 2 which is
arranged between the first layer 1 and the third layer 3 is made of a
material that is different from the material of the first layer 1 and the
third layer 3. The material of the first layer 1 and the third layer 3
may be aluminum and the material of the second layer 2 may be titanium.
As shown in FIG. 1, the geometrical dimensions of the first layer 1 and
the third layer 3 are identical such that a symmetrical impression of the
composition of the layered structure 10 may be obtained. The layered
structure 10 may be manufactured by additive layer manufacturing and/or
selective laser melting such that, after connecting the different layers
of the layered structure 10, a metallic continuity between the layers can
be achieved; e. g. the different layers may be firmly bonded. When
changing the temperature of the layered structure 10, e. g. when cooling
the layered structure 10 after the manufacturing process, internal
stresses are generated within the layered structure 10 because titanium
and aluminum have different coefficients of thermal expansion. In other
words, titanium has a smaller thermal expansion or elongation than
aluminum when equally changing the temperature of both materials which
leads to internal stresses within every layer of the layered structure
10.

[0059] FIG. 2 shows cross-sectional view of a layered structure 10 with an
unsymmetrical design in which the first layer 1 is thicker than the third
layer 3. In this example the first layer 1 and the third layer 3 are made
of aluminum and the second layer 2, which is located between the first
layer 1 and the third layer 3, is made of titanium. The layered structure
10 may as well be manufactured using additive layer manufacturing and/or
selective laser melting such that a metallic continuity is provided
between the first layer 1 and the second layer 2 as well as between the
second layer 2 and the third layer 3. However, the different layers may
be firmly bonded. In this manner, it is possible that a internal stress
within the layered structure 10 is induced or generated if the
temperature of the layered structure 10 is changed. This is due to the
different coefficients of thermal expansion or the expansion
characteristics of different materials. In this case, titanium has a
lower coefficient of thermal expansion than aluminum.

[0060] As a result of the induced internal stresses, the layered structure
10 may be deformed, as shown in FIG. 3. The deformation may appear as a
bending or twisting of the layered structure 10. The cross-sectional view
in FIG. 3 indicates a bending of the layered structure 10. The bending is
generated by internal stresses being induced by the firmly bonded
arrangement of layers of the layered structure 10 combined with changes
in temperature to which the layered structure 10 is subjected. For
example, the layered structure 10 is not bent when it is manufactured by
additive layer manufacturing at relatively high temperatures whereas a
bending, as shown in FIG. 3, occurs when cooling the layered structure 10
to environmental conditions. In this case, the first layer 1 is thicker
than the second layer 2 and the third layer 3. The unsymmetrical
arrangement of the different layers may induce internal stresses within
the layered structure 10 and the occurrence of internal stresses in turn
results in the bending visualized in FIG. 3. By the method for
manufacturing the shell-like structural component using additive layer
manufacturing, a predetermined bending of the layered structure 10 may be
achieved such that a predetermined deflection as a result of the bending
of the layered structure 10 is provided. This deflection may
advantageously compensate a deformation which is due to external loads.

[0061] FIG. 4 shows a sectional view of a shell-like structural component
in a loaded condition 21 and in an unloaded condition 20, wherein the
shell-like structural component is attached to two beams 23a, 23b. A
first end of the shell-like structural component is attached to a first
beam 23a and a second end of the shell-like structural component is
attached to a second beam 23b. It should be mentioned that the items
shown in FIG. 4 are three-dimensional objects, like for instance a cargo
floor panel that is supported by two beams 23a, 23b. The beams, which are
also called cross beams, may be extruded aluminum profiles connected by
friction stir welding. A front view of this arrangement is chosen for
simplicity. In the unloaded condition 20, the shell-like structural
component is bent in such a way that at least a part of it is deflected
into a first direction 24 which indicated by an arrow. Thus the first
direction 24 indicates the bending direction. This bending is due to
internal stresses induced by providing different materials within a
certain region or certain regions of the shell-like structural component
which for instance comprises a layered structure. If an external load is
applied to the shell-like structural component in a second direction 22
which is indicated by another arrow, the shell-like structural component
is pushed into the second direction 22 opposite to the first direction
24. In other words the bending direction 24 is substantially parallel
and/or opposite to the loading direction 22. However, in the loaded
condition 21, the deflection or bending of the shell-like structural
component may be reduced. The loaded condition 21 visualized in FIG. 4
indicates that the bending or the deflection of the shell-like structural
component may even vanish if a distinct load is reached. The internal
stresses may be induced within the shell-like structural component such
that a predetermined bending or deflection occurs when a certain force or
load is applied to the shell-like structural component in the loaded
condition 21. In other words, the internal stresses within the shell-like
structural component and hence the bending of the shell-like structural
component may be adapted by using the described manufacturing method.
Applying the first material to well-chosen regions of the shell-like
structural component by additive layer manufacturing, provides the
possibility to predetermine the deformation and with it the bending of
the shell-like structural component with respect to changes of
environmental conditions, such as pressure differences or temperature
differences. Therefore, the shell-like structural component may adopt a
shape which provides enhanced operating conditions of the vehicle into
which the shell-like structural component is integrated.

[0062] FIG. 5A shows sectional view of two stiffening units 32 and a part
of an outer skin 30 of an aircraft fuselage in an unloaded condition 20
and FIG. 5B shows the same in a loaded condition 21. For simplicity, the
stiffening units 32 are drawn as if they are detached from the outer skin
30. In a ready-made aircraft fuselage, the stiffening units 32 are
attached to the outer skin 30. The stiffening units 32 may be stringers
or ribs. The part of the outer skin 30 may be the shell-like structural
component which is manufactured by the described method. In the unloaded
condition 20 the shell-like structural component is bent or deformed such
that a corrugated shape is adopted. This corrugated shape is the result
of the internal stresses induced by the manufacturing process of the
shell-like structural component. An ideal contour 31 is also shown in
FIG. 5A. The ideal contour 31 describes a condition of the part of the
outer skin 30 which is characterized by a reduced drag during flight of
the aircraft. This ideal contour 31 is adopted by the part of the outer
skin 30 in the loaded condition 21 which is described in FIG. 5B. The
pressure difference between the inside of the aircraft fuselage and the
outside of the aircraft fuselage during cruise flight causes a load on
the part of outer skin 30 such that a linear shape of the part of the
outer skin 30 is adapted. The part of the outer skin 30 may substantially
be aligned with the ideal contour 31 such that, in a loaded condition 21,
a reduced drag can be achieved. Generally, the deformation of the part of
the outer skin 30, which may be the shell-like structural component, may
be generated by internal stresses within the part of the outer skin 30
induced by the described method such that the part of the outer skin 30
adopts an aerodynamically improved shape if a certain pressure difference
or temperature change is reached; e. g. the part of the outer skin 30
follows the ideal contour 31.

[0063] FIG. 6A shows a cross-sectional view of an aircraft fuselage with
an integrated aircraft door 40 in an unloaded condition 20. Moreover, a
floor 43 within the aircraft fuselage as well as an outer skin 41 of the
aircraft fuselage is indicated. The aircraft door 40 may be the
shell-like structural component which is manufactured by the described
method. The door 40 may be slightly bent in the unloaded condition 20 as
shown in FIG. 6A. It is noted that the illustration of the shape of the
door is strongly exaggerated. The door 40 may be manufactured by the
method, such that, if a predetermined load is applied to the door 40 in a
loaded condition 21, it is deformed or bent and therefore substantially
aligned with the contour of the outer skin 41 of the aircraft fuselage.
The loaded condition 21 is shown in the cross-sectional view of FIG. 6B.
In the loaded condition 21 the door 40 is pushed from the inside towards
the outside with respect to the aircraft fuselage. This may positively
influence the aerodynamic characteristics of the aircraft in a region
near the door 40. The principle may generally apply to other structural
components of an aircraft, such as a pressure bulkhead. It should be
understood that the inside of an aircraft fuselage describes the part of
an aircraft which is enclosed by the surrounding outer skin 41 whereas
the outside describes the environment surrounding the outer skin 41 or
the aircraft fuselage.

[0064] FIG. 7A schematically shows a first aircraft 50 with aircraft wings
in an unloaded condition 20 and in a loaded condition 21. The first
aircraft 50 may be a conventional passenger aircraft. In the unloaded
condition 20, e. g. during ground operation, the wings of the first
aircraft 50 may adapt the shape indicated by the dashed lines in FIG. 7A.
This shape represents an ideal contour which is provided by
conventionally manufacturing or assembling the aircraft wings. In the
loaded condition 21, e. g. during cruise flight, the wings of the first
aircraft 50 are bent or deflected in a vertical direction of the first
aircraft 50 such that a deviation from the ideal contour is caused.

[0065] In contrast, FIG. 7B schematically shows a second aircraft 51 with
aircraft wings in an unloaded condition 20 and in a loaded condition 21,
the wings being manufactured by the method according to the embodiment.
Therefore, shell-like structural components may be integrated into the
wings such that, in the unloaded condition 20, e. g. during ground
operation, a bending or deflection of the wings is generated as a result
of internal stresses generated by the manufacturing method. The shape or
contour of the wings in the unloaded condition 20 is indicated by dashed
lines in FIG. 7B. In the loaded condition 21 of the wings of the second
aircraft 51, e. g. during cruise flight, the wings may adapt a shape
which is substantially equal to the ideal contour. The adaption may be
supported by a bending or deflection which is caused by temperature
differences between ground operation and cruise flight. The bending may
be significantly influenced by temperature differences since the
shell-like structural components may comprise different materials, each
having distinct coefficients of thermal expansion. In other words, the
wings may substantially be adapted to the ideal contour with minimum drag
if a certain load in combination with a certain temperature is reached
during cruise flight. Adapting the ideal contour of the wings in the
loaded condition 21, results in a drag count reduction during cruise
flight of the second aircraft 51. This principle may also be used for
other applications in which a deformation and bending of shell-like
structural components, which are integrated in a vehicle, leads to
enhanced aerodynamic characteristics.

[0066] For example, FIG. 8A schematically shows a side view of an aircraft
fuselage in an unloaded condition 20. The unloaded condition 20, e. g.
during ground operation, is characterized by an ideal contour or shape of
the fuselage which would provide a good aerodynamic behavior of the
fuselage. This ideal contour or shape is usually not existent anymore
during flight since the aircraft fuselage becomes deformed due to
external loads, as shown in FIG. 8B. The external loads may for instance
be lift forces predominantly acting on the wings. The external loads
change the shape of the whole fuselage. This deformation of the fuselage
may result in a reduced aerodynamic efficiency. However, the embodiment
provides a method for manufacturing shell-like-structural components
which may be integrated into the aircraft fuselage, for example as parts
of the outer skin 30, such that a deformation or bending of the fuselage
in an unloaded condition 20 is generated. This aspect is visualized in
FIG. 8C, which shows the aircraft fuselage in an unloaded condition 20,
for example after assembling the fuselage on the ground. The generated
bending in the unloaded condition 20 may lead to an adaption of the
fuselage shape to said ideal contour or shape, as shown in FIG. 8A, in
the loaded condition 21. The aerodynamic efficiency in the loaded
condition 21, e. g. during flight, may be enhanced by the adaption of the
fuselage to the ideal shape. Adaption of the ideal contour or shape means
that the induced bending of the fuselage after assembling on the ground
is reduced during flight operation.

[0067] FIG. 9 shows a method for manufacturing a shell-like structural
component for a vehicle using additive layer manufacturing and/or
selective laser melting. The method comprises different steps. In a step
S1 of the method, a first material is applied to a region of the
shell-like structural component. In another step S2, the region of the
shell-like structural component is heated by a laser beam such that the
first material is added to the shell-like structural component. For
example, a powder bed on the shell-like structural component is heated
before applying or printing the first material to the shell-like
structural component. The shell-like structural component which comprises
the first material is cooled in another step S3 such that an internal
stress is generated within the shell-like structural component resulting
in a bending of the shell-like structural component. The method may
comprise further steps, like for instance changing a temperature and/or a
pressure difference such that the shell-like structural component adopts
a predetermined geometrical shape.

[0068] Applying the first material to the region of the shell-like
structural component may be conducted in a multi-direction additive
manufacturing process in which the first material is simultaneously
applied from different directions and/or to different regions of the
shell-like structural component. This provides an accelerated
manufacturing of the shell-like structural component.

[0069] It should be understood that the first material may be applied onto
the surface of the shell-like structural component as well as into the
shell-like structural component. Thus, it is also possible that the first
material is enclosed by the shell-like structural component, for example
in a layered structure. In other words, the first material is comprised
by the shell-like structural component.

[0070] The method also provides an additive repair process for filling
dents or scratches on the surface of the shell-like structural component.
The dents or scratches may be filled with Scalmalloy which is an alloy
comprising aluminum, magnesium and scandium. Thus, it may not be
necessary that the material on the surface of the shell-like structural
component has to be removed or scraped by subtractive processes until the
dents or scratches vanish.

[0071] While the embodiments have been illustrated and described in detail
in the drawings and the foregoing description, such illustration and
description are to be considered illustrative and exemplary and not
restrictive; the embodiments are not limited to the disclosed
embodiments. Other variations to the disclosed embodiments can be
understood and effected by those skilled in the art and practicing the
claimed embodiment, from a study of the drawings, the disclosure, and the
appended claims. In the claims the term "comprising" does not exclude
other elements, and the indefinite article "a" or "an" does not exclude a
plurality. The mere fact that certain measures are recited in mutually
different dependant claims does not indicate that a combination of these
measures cannot be used to advantage. Any reference signs in the claims
should not be construed as limiting the scope of protection.

[0072] While at least one exemplary embodiment has been presented in the
foregoing detailed description, it should be appreciated that a vast
number of variations exist. It should also be appreciated that the
exemplary embodiment or exemplary embodiments are only examples, and are
not intended to limit the scope, applicability, or configuration of the
embodiment in any way. Rather, the foregoing detailed description will
provide those skilled in the art with a convenient road map for
implementing an exemplary embodiment, it being understood that various
changes may be made in the function and arrangement of elements described
in an exemplary embodiment without departing from the scope of the
embodiment as set forth in the appended claims and their legal
equivalents.